The conventional cable structure includes conductor(s), an insulating layer and a cover layer. The conductor(s) are clad in the insulating layer, and the insulating layer is clad in the cover layer. Generally, the cover layer is formed from plastics having a Mohs hardness between 2.0 and 2.5, and cannot provide a bite-resistant effect. However, an outdoor cable is often bitten by pests such as termites and rodents. Once the insulating layer and the cover layer are bitten through, the innermost conductor(s) would be exposed. Thus, a short circuit fault of the cable may easily occur and even cause fire hazards. This may result in serious damage.
In order to prevent the cable from biting by pests such as termites and rodents, the main protection means used in the current industry includes physical and chemical methods. The physical method is using a high hardness plastic (e.g., nylon) to form the cover layer of the cable. The resulting cover layer having high hardness, good toughness and high surface gloss can achieve a bite-resistant effect. Furthermore, a rigid protection layer can be disposed inside the cover layer to increase the bite-resistant effect. In addition, the chemical method is adding a repellent agent (e.g., chlordane, aldrin and dieldrin) in the cover layer or coating a layer containing the repellent agent on the surface of the cover layer. Accordingly, the cable can have an odor or a viscosity which pests such as termites and rodents fear or hate.
Although the physical method does not harm the human body and the environment, and has a long and effective time of preventing bites, the hard plastic or rigid material may cause an increase in weight, difficulties in installing the cable, a complicated production process, and high cost. For example, in the case of using nylon to form the cover layer of the cable, the production process is more complicated and requires a nylon-specific extrusion machine, which would cause high costs. In addition, when the chemical method is used to prevent the cable from biting by termites or rodents, the repellent agent not only releases highly toxic substances in the production process, which are difficult to be decomposed, but causes a great threat to the human body and the environment.
Therefore, how the problems resulting from the conventional cable structure can be solved, and how a cable structure having good anti-rodent and anti-termite functions can be provided has become an apparent issue to those skilled in the art.